How do you handle Commerce package upgrades?

[ZackL]

So I'm new to e-commerce. I bought the 'Commerce' addon for my community to handle donations when we upgraded to v4 and haven't really touched the store stuff much. So my knowledge is a bit limited.

My use case is I have 4 packages (let's call them Packages A through D). I also have a 5th package that is a basic package that's free for an entry-tier item. All packages are of the same tier and reside in the same product category and all represent basically the same product, just different levels. Like hosting packages, except I'm not using WHM (just normal products).

The way I'm envisioning how potential customers interact with these products is this: Purchase any of the products (A-D) and disallow purchasing of other similar products; basically, only allow changing via upgrading existing package or cancelling.

I'm unsure how to do this.  

 

Thanks in advance.